📖 Chapter 4 of 8 · Green Energy - Basic 2 · Class 7
Chapter 4: How Do Wind and Water Turn into Electricity?
In this chapter
- The two big helpers: the turbine and the generator.
- What happens inside a wind turbine.
- Big dams and small streams that make electricity.
- Meet Harpreet from Punjab and Tashi from Sikkim.
The Big Idea
Wind power and water power both use a turbine and a generator. Moving air or falling water pushes the blades of the turbine and makes it spin. The spinning shaft turns magnets inside the generator, close to coils of copper wire. When a magnet moves near a coil, electricity starts to flow in the wire!
Did You Know?
The idea that a moving magnet can make electricity was discovered by the scientist Michael Faraday in 1831. Almost every power plant in the world still uses his idea today.
Story Time — Harpreet and the Wall That Holds a Lake
Harpreet, age 10 · Rupnagar, Punjab
Harpreet lives in Rupnagar, Punjab, near the Sutlej river. On a school holiday, his Chachaji (uncle), who is an engineer, took him to see the Bhakra dam, just across the border in Himachal Pradesh.
Harpreet’s mouth fell open. A giant concrete wall stood between two mountains. Behind it lay a huge lake called Gobind Sagar. “Chachaji, why hold back so much water?”
“Because high water has stored energy,” Chachaji explained. “We let it rush down through big tunnels. The falling water spins turbines in the power house, and the turbines turn generators that make electricity.”
“What happens to the water after that?” asked Harpreet. “It flows on into canals that carry it to farms across Punjab, Haryana and Rajasthan. The same water makes power first and then helps grow wheat and rice!”
On the way home, Harpreet watched the canal flowing beside the road. “So the water in our fields has already done a job before it reached us!” Chachaji laughed. “Yes, it is the hardest-working water in India.”
Story Time — Tashi’s Stream That Lights the Village
Tashi, age 9 · A hill village in South Sikkim
Tashi lives in a green hill village in Sikkim. Snowy peaks shine in the distance, and a cold stream rushes past his school. Near the monastery, the stream turns a big prayer wheel all day and night.
One morning, his teacher, Pem Madam, took the class down to the stream. “This water has been turning our prayer wheel for years. Today I will show you how it can also light our homes.”
A little further down stood a small hut with a metal wheel beside it. Water from the stream was guided into a pipe and made to fall onto the wheel, spinning it fast. “This is a micro hydro plant,” said Pem Madam. “The spinning wheel turns a small generator inside the hut.”
Tashi followed the wires with his eyes. They ran up the hill to the houses. “No big dam is needed?” he asked. “Not for a village,” she said. “A fast mountain stream is enough, and the water goes back into the stream.”
That night, as the lights glowed in his home, Tashi whispered, “Thank you, little stream.” He decided he would always keep it clean.
Inside a Wind Turbine
A wind turbine and a water turbine work in almost the same way. Follow the numbers.
- 1. Blades catch the wind. They are shaped a little like aeroplane wings, so moving air pushes them round.
- 2. The shaft spins. The blades are joined to a long rod called a shaft. Gears can make it spin faster.
- 3. Magnets spin near coils. Inside the generator, magnets turn close to coils of copper wire.
- 4. Electricity flows. The moving magnets make current flow in the wire, which goes down the tower to the power lines.
- Why so tall? Wind is stronger and steadier high above the ground, away from trees and buildings.
Big dams: Tehri dam in Uttarakhand is about 260 metres tall — roughly as tall as an 80-storey building! Big dams give clean power, but they also flood land and change rivers, so they must be planned carefully.
Solved Examples
Think first, then read the answer.
1. What are the two main parts that make electricity from wind or water?
Show answer
Answer: The turbine, which is spun by wind or water, and the generator, where spinning magnets make electricity flow in copper coils.
2. Why are dams usually built in hilly areas?
Show answer
Answer: In hills, water can be stored high up. When it falls from a greater height, it moves faster and spins the turbines with more force.
3. Give one good thing and one problem of big dams.
Show answer
Answer: Good: clean electricity and water for farms. Problem: land, forests and villages can go under water, and river animals are affected.
4. How is a micro hydro plant different from a big dam?
Show answer
Answer: It is small, uses the natural flow of a stream without a giant wall, and makes enough power for a village rather than for many cities.
5. A wind turbine makes 5,000 units in a day. A home uses 5 units a day. How many homes can it power for that day?
Show answer
Answer: 5,000 ÷ 5 = 1,000 homes.
✎ Now You Try!
The blades of a wind turbine turn 20 times in one minute. How many times will they turn in 5 minutes? In 1 hour?
Check Your Understanding
A. Fill in the blanks
- Wind and water both spin a .
- Inside a generator, magnets spin near coils of wire.
- The Bhakra dam is built on the river.
- A small power plant on a stream is called a hydro plant.
- Michael discovered that moving magnets can make electricity.
B. True or False
- Wind is usually stronger high above the ground. ( ___ )
- Water from Bhakra dam also helps farms. ( ___ )
- Big dams have no effect on rivers or people. ( ___ )
- A turbine and a generator work together. ( ___ )
C. Choose the correct option
- The rod joined to the blades is the (a) shaft (b) coil (c) cable
- Gobind Sagar is a (a) river (b) lake behind a dam (c) hill
- Tashi’s village gets power from a (a) coal plant (b) stream (c) desert
D. Answer in two or three sentences
- Explain how falling water makes electricity at a dam.
- Why did Tashi decide to keep the stream clean?
- Draw and label the four main parts of a wind turbine.
Brain Buster
Blow on a paper pinwheel softly, then hard. What changes? What does this tell you about strong winds?
Check your understanding
Tap an answer to see if it is correct. This is just for fun — nothing is saved.
1. Which two parts work together to make electricity from wind or water?
- Turbine and generator
- Pipe and tap
- Battery and bulb
Show answer
A. Turbine and generator
2. What happens inside a generator?
- Water is boiled
- Magnets spin near coils of copper wire
- Sand is heated
Show answer
B. Magnets spin near coils of copper wire
3. Why are wind turbines built so tall?
- To look nice
- Wind is stronger and steadier high up
- To reach the clouds
Show answer
B. Wind is stronger and steadier high up
4. Where did the water go after spinning the turbines at Bhakra?
- Into canals for farms
- Back up the mountain
- Into the sky
Show answer
A. Into canals for farms